This Is the Largest Moon in the Solar System

By Douglas A. McIntyre Published Oct 15, 2:00PM EDT

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This Is the Largest Moon in the Solar System — © By Apollo 17 Picture of the Whole Earth: NASATelescopic Image of the Full Moon: Gregory H. Revera - The Earth seen from Apollo 17.jpgFullMoon2010.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=39083086

There are 214 moons in our solar system. Of these, 158 are confirmed and another 56 are provisional, meaning scientists suspect a moon exists or the moon has been seen only once. Of the 16 moons that have mean diameters of over 1,000 kilometers, four orbit Jupiter, four orbit Saturn, and four orbit Uranus.

The largest moon in the solar system is Ganymede, which orbits Jupiter. It measures 5,262 mean km and is followed closely in size by Titan, which orbits Saturn and measures 5,150 mean km. (A kilometer is roughly 0.62 miles.) Ganymede (pronounced “GAN uh meed”) is the ninth-largest object in the solar system, about 41% the size of Earth.

Ganymede is the only moon in our solar system with its own magnetic field. “The magnetic field causes auroras, which are ribbons of glowing, electrified gas, in regions circling the moon’s north and south poles,” according to the NASA Solar System Explorer.

Galileo Galilei discovered Ganymede on Jan. 7, 1670. It was named after a cupbearer of the Greek god Zeus, who was known as Jupiter to the Romans. Galileo originally thought Ganymede might be a star. These are the most unforgettable moments in space exploration.

Ganymede completes an orbit of Jupiter every seven days and three hours. It is made up of rock and frozen water in roughly equal parts. Frozen ice covers almost its entire surface.

According to The New York Times, the NASA Galileo spacecraft found what may have been water under the surface of this ice. The spacecraft flew by Ganymede six times between 1996 and 2000. JUpiter ICy moons Explorer will reach Jupiter in July 2031 and will spend four years exploring Jupiter and three of its moons: Ganymede, Callisto, and Europa. Here are 30 NASA inventions we still use everyday.

Click here to see the largest moon in the solar system

16. Tethys
> Planet: Saturn
> Mean diameter: 1,066 km

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15. Dione
> Planet: Saturn
> Mean diameter: 1,123 km

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14. Ariel
> Planet: Uranus
> Mean diameter: 1,158 km

13. Umbriel
> Planet: Uranus
> Mean diameter: 1,169 km

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12. Charon
> Planet: Pluto
> Mean diameter: 1,207 km

11. Iapetus
> Planet: Saturn
> Mean diameter: 1,471 km

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10. Oberon
> Planet: Uranus
> Mean diameter: 1,523 km

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9. Rhea
> Planet: Saturn
> Mean diameter: 1,529 km

8. Titania
> Planet: Uranus
> Mean diameter: 1,578 km

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7. Triton
> Planet: Neptune
> Mean diameter: 2,707 km

6. Europa
> Planet: Jupiter
> Mean diameter: 3,122 km

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5. Moon
> Planet: Earth
> Mean diameter: 3,475 km

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4. Io
> Planet: Jupiter
> Mean diameter: 3,643 km

3. Callisto
> Planet: Jupiter
> Mean diameter: 4,821 km

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2. Titan
> Planet: Saturn
> Mean diameter: 5,150 km

1. Ganymede
> Planet: Jupiter
> Mean diameter: 5,262 km

About the Author Douglas A. McIntyre →

Douglas A. McIntyre is the co-founder, chief executive officer and editor in chief of 24/7 Wall St. and 24/7 Tempo. He has held these jobs since 2006.

McIntyre has written thousands of articles for 24/7 Wall St. He is an expert on corporate finance, the automotive industry, media companies and international finance. He has edited articles on national demographics, sports, personal income and travel.

His work has been quoted or mentioned in The New York Times, The Wall Street Journal, Los Angeles Times, The Washington Post, NBC News, Time, The New Yorker, HuffPost USA Today, Business Insider, Yahoo, AOL, MarketWatch, The Atlantic, Bloomberg, New York Post, Chicago Tribune, Forbes, The Guardian and many other major publications. McIntyre has been a guest on CNBC, the BBC and television and radio stations across the country.

A magna cum laude graduate of Harvard College, McIntyre also was president of The Harvard Advocate. Founded in 1866, the Advocate is the oldest college publication in the United States.

TheStreet.com, Comps.com and Edgar Online are some of the public companies for which McIntyre served on the board of directors. He was a Vicinity Corporation board member when the company was sold to Microsoft in 2002. He served on the audit committees of some of these companies.

McIntyre has been the CEO of FutureSource, a provider of trading terminals and news to commodities and futures traders. He was president of Switchboard, the online phone directory company. He served as chairman and CEO of On2 Technologies, the video compression company that provided video compression software for Adobe’s Flash. Google bought On2 in 2009.